Intellectual Merit. The development of the piston-cylinder apparatus in the 1960s revolutionized the study of the Earth's interior, allowing simulation of conditions in the Earth's upper mantle. Popularization of the multi-anvil device in the 80's extended petrology's reach to the top of the lower mantle (down to 750 km depth). Today, advances in laser-heated diamond anvil cell (DAC) and chemical analyses at the nano-scale open new opportunities for studying geophysical and geochemical problems related to the Earth's deep interior to greater than 100 GPa - all the way to the core. The goal of this proposal is to establish the laser-heated DAC as a tool to study chemical mass transfer under extreme conditions such as those found at the core-mantle boundary (CMB). We propose a "proof of concept" and technique development study to lay the groundwork for more extensive investigations. Specific projects include (1) Ni, Co partitioning between liquid metal and liquid silicate, and (2) Re, Pt, Os partitioning between solid Fe and Fe-S melt. We expect the experiments to range up to 100 GPa in pressure, allowing us to place experimental constraints on the depth of an hypothesized magma ocean during formation of the Earth, and the geochemical signatures that may reflect the chemistry of CMB and the Earth's core.
Broad Impacts. The proposed research will open new research opportunities at the interface of petrology, mineral physics, geochemistry, and geophysics, and produce high-quality data that are necessary for understanding the interior of the Earth and develop new cutting-edge research frontiers. The project will involve training of graduate students and postdoctoral associates and provide them with competitive research experience. The expected results will have broad impact in many different fields including experimental petrology, geochemistry, geophysics, mineral physics, and geodynamics. Further, this collaboration between the Carnegie Institution and the Smithsonian, National Museum of Natural History, ensures that the results will be disseminated to the lay-public, K-12 students, members of congress, and philanthropists, and placed within a broader context to promote Earth science research and increase the visibility of the Earth sciences in the public domain.
The composition of Earth's metal core, and the mechanism by which the core formed approximately 4.56 billion years ago are unknowns. This project sought to constrain the mechanism of core formation by developing novel techniques in the Laser-Heated Diamond Anvil Cell (LHDAC) to equilibrate siliates (proxy for Earth's mantle) and metals (proxy for Earth's core) at the pressures and temperatures relevant to core formation. Moreover, we sought to recover the experimental charges for chemical analysis using nano-Secondary Ion Mass Spectrometry (nanoSIMS) to determine whether metal/silicate trace element partioning at high pressure and temperature is consistent with equilibrium core formation models. We created standards for nanoSIMS and successfully carried out and recovered high pressure-temperature LHDAC experiments. We find that Ni partitioning is consistent with equilibrium models of core formation. The procedures developed during this project represent major technical advances for the field and contribute to the broader impacts of this project. Moreover, this award was fundamental in establishing a new high pressure lab at the Smithsonian Institution that has since supported three postdocs and led to several peer-reviewed publications. This award also partially funded the stipends of two postdoctoral fellows, Dr. Angele Ricolleau and Dr. Chris Seagle and thus contributes to training the next generation of Earth Scientists.
